I bought a PICO 2203 about one year ago, but starded to use it juste a few weeks ago. Everything works fine except distortion analysis

To show you the problem I've done two tests :a) with a very low distortion sinus generator (Marconi TF 2005R), an HP8903 distortion analyseur (witch cane give me TRS and TDH (in %)) in one hand, and the Pico2203 (using same cable than with HP8903) one the other hand.- the THD value given for a 200Hz signal is : HP : 0,07 PICO : 0,78- the THD value given for a 633Hz signal is : HP : 0,038 PICO : 0,157- the THD value given for a 6kHz signal is : HP : 0,033 PICO : 0,229RMS and frequency values are the same with HP and PICO.The Pico FFT analyzer gives me the folowing screens (Hanning window) :200Hz signal :

633Hz signal :

b) with the Pico AWG (at 600Hz) with signal out shorted with channel A (using the same cable as before and Hanning window) :

As ou can see something is wrong... Is this due to sofware or hardware???

From the post you sent I can tell that you have put averaging on (picture says it!), but I require more information about your setup. For example you say Hanning Window do you mean Hamming or do you mean Hann window? Also what is the amplitude of the signal that you are feeding in.

Also you seem to have a big frequency span across your signal, 5MHz, I would drop the frequency range down to say something like 9.766 kHz or lower.

Could you send a settings file?

Bear in mind this is an 8 bit oscilloscope and not a dedicated spectrum analyser.

Try using a repeat trigger instead of an auto trigger as you may be getting skewed results due to hysteresis, particularly on the larger voltage ranges, +/-20V.

In terms of your two signals try using the same voltage range, it looks to me like you are using channel A on +/-1V and channel 2 on +/-2V.

In terms of your second post sent on Monday, the signal generator on the 2203 is NOT a low distortion sine oscillator and therefore it will have noise on it, its NOT meant to replace a dedicated signal generator, particularly a low distortion one.

Some of the higher end products will have better signal generators but none of them will be as good as a dedicated signal generator.

The harmonics you see are because of the fact that the scope is an 8bits that when sold was less than £200. The other thing I notice is that you are using +/-10V signal on a +/-1.5V signal why are you not using +/-2V?

The scope itself is an entry level scope you really need to use something like the 4262 oscilloscope This is a 16 bit oscilloscope and has a significantly better sine wave generator.

Please see attached image of a 4262 with same settings, 1.7kHz +/-3V signal, Averaging and Han Window with a spectrum range of 100kHz.

thanks a lot (especially for the last picture)... Now everything is clear : my problem is the fact that the 2203 is an 8bits, and an entry level scope (as you say), and nothing else!A 4262 would be the solution, but since my use is not a professional one, the cost of the 4262 is a problem I must find another solution...